Image and Fluoroscopy Area Dose Product Attribute

X-Ray dose, measured in dGy*cm*cm, to which the patient was exposed for the acquisition of the entire Irradiation Event from which this image was reconstructed.

Note

All of the images reconstructed from the same Irradiation Event will have the same value for this Attribute, which is the total for the Irradiation Event, which is repeated in each image, regardless of whether or not the Irradiation Event UID (0008,3010) is present with a value in the Multi-frame Dimension Module. I.e., the values for each image should not be summed. The sum of the area dose products of all encoded Irradiation Events may not result in the total area dose product to which the patient was exposed.

This may be an estimated value based on assumptions about the patient’s body size and habitus.

Multi-frame Dimension Module

C.7.6.17 Multi-frame Dimension Module

The Multi-frame Dimension Module contains a sequence with items pointing to attributes defining a set of dimensions that are usually known prior to the acquisition commencing. It is up to the generating applications to decide what attributes are important to describe the multi-frame dimensions.

The application that generates the Concatenation or SOP Instances may use the order of Dimension Index Pointers (0020,9165) in the Dimension Index Sequence (0020,9222) to guide the receiving application in determining the order of the presentation of image frames. The first index has the highest ranking, the next index has a lower ranking, etc. Frames with higher values for the dimension with the highest ranking would only be presented after all frames that have values for Dimension Index Pointers (0020,9165) of the lower rankings have been presented.

If the set of Dimension Index Pointers does not provide an attribute set whose values are unique for each frame then the order for the frames with the same value set will be incompletely specified. The receiving application could use the logical frame number to resolve this ambiguity. If the attribute set contains more dimensions than are needed to specify a unique ordering, the lower order ranking attribute(s) will have no effect on the ordering.

Note

For example if there were the following indices in the following order:

The actual order of the frames in the object is up to the generating application.

If the effective echo time was not included in the Dimension Index Pointers in the above example then the order of sorting for the frames with the same indices will be undefined - in this case there would be 2 frames with the index set (Stack ID, In-stack Position) = (1,1) and the order of these frames is not specified.

If there were another attribute appended to the Dimension Index Pointers, for example TR, then the TR index would not be used in determining the order of the frames. So the Index Frame Pointers would contain (Stack ID, In-stack Position, Effective Echo Time, TR) but the TR index would be irrelevant for frame ordering purposes.

Required if the value of Dimension Index Pointer (0020,9165) is the Data Element Tag of an Attribute that is contained within a Functional Group Sequence.

>Functional Group Private Creator

(0020,9238)

1C

Identification of the creator of a group of private data elements.

Required if the Functional Group Pointer 0020,9167) value is the Data Element Tag of a Private Attribute.

>Dimension Organization UID

(0020,9164)

1

Uniquely identifies a set of dimensions referenced within the containing SOP Instance. In particular the dimension described by this sequence item is associated with this Dimension Organization UID. See Section C.7.6.17.2 for further explanation.

>Dimension Description Label

(0020,9421)

3

Free text description that explains the meaning of the dimension.

C.7.6.17.1 Dimension Indices

With the Dimension Index Sequence (0020,9222), Data Element Tags are specified that identify the indices used for a particular SOP Instance.

The actual index values for each frame in a multi-frame header are stored in a single Dimension Index Values Attribute (0020,9157) defined in the Frame Content Functional Group. For each SOP Instance this Attribute has a Value Multiplicity equal to the number of Items in the Sequence. The ordering of the Items in the Sequence defines the ordering in the Dimension Index Values Attribute: Item 1 of the Sequence relates to Value 1, Item 2 to Value 2, etc.

The Dimension Index Pointer (0020,9165) references a single Attribute that describes the actual values that define the dimension. Each Attribute referenced in the Dimension Index Sequence (0020,9222) will have an index stored in the Dimension Index Values (0020,9157) for each frame. Each index value is an ordinal number starting from 1 and monotonically increasing by 1 within the scope of a Dimension Organization UID (0020,9164). These values are independent of the actual values of the attribute referenced by the Dimension Index Pointer (0020,9165), i.e., the index values are logical indices, rather than actual indices. Frames assigned the same index shall contain nominally the same value for the referenced Attribute. If the referenced Attribute is not present for some frames, or is present but has no value, then a single index shall be assigned to indicate the lack of the value (i.e., all such frames shall have the same index value, which is different from other
index values). It is at the discretion of the SOP Instance creator whether the Attribute values are equivalent, and therefore appropriate for assignment to the same index value.

Note

Dimension Index Pointer (0020,9165) may point to a Sequence containing a Functional Group. In that case all the Attributes of the Sequence are associated with the index value.

The Dimension Index Pointer (0020,9165) may point to a Data Element Tag (gggg,eeee) that is not present for all frames of an object, or does not have a value for all frames of an object. For such frames, index values are still assigned, as described above.

The indices used in the Dimension Index Values (0020,9157) may or may not be identical to the value of indexed attribute referenced by Dimension Index Pointer (0020,9165). For example, if the referenced Attribute is itself encoded in an index-like fashion (being an ordinal number starting from 1), such as In-Stack Position Number (0020,9057), then index value 1 would typically correspond to In-Stack Position Number (0020,9057) value 1. On the other hand, if the referenced attribute encodes some physical measure, such as a time or distance, or a categorical value, such as a string describing the phase of contrast, or a more complex description such as an entire functional group, then the index value is independent of the encoded value.

The scope of the values of Dimension Index Pointer (0020,9165) is defined to be within a single Dimension Organization UID (0020,9164). If the same Dimension Organization UID (0020,9164) is present in multiple Instances (whether part of a Concatenation or not), at least one of those Instances (though not necessarily every Instance) will contain a value of 1 for the Dimension Index Values (0020,9157).

The Functional Group Pointer (0020,9167) value is the Data Element Tag (gggg,eeee) of the Functional Group Sequence that contains the Attribute being indexed. If the Dimension Index Pointer 0020,9165) contains a Data Element Tag that identifies a Functional Group Sequence then the Functional Group Pointer (0020,9167) shall not be present.

If the Functional Group Pointer (0020,9167) attribute contains a Private Data Element, then the Functional Group Private Creator (0020,9238) shall contain the Private Creator of the block of Private Data Elements.

Note

An example of the usage of the Dimension Index Sequence (0020,9222) and Dimension Index Values (0020,9157) attributes:

Dimension Index Sequence (0020,9222) specifies two indices:

Cardiac Trigger Delay Time (0020,9153)

Image Position (Patient) (0020,0032)

The Dimension Index Sequence (0020,9222) is filled with the following contents:

Item

Attribute

Value

1

Dimension Index Pointer

(0020,9153)

Functional Group Pointer

(0018,9118)

…

2

Dimension Index Pointer

(0020,0032)

Functional Group Pointer

(0020,9113)

…

The Dimension Index Values (0020,9157) (in the Frame Content Functional Group) for each frame consists of two values:

Index of Cardiac Trigger Delay Time \ Index of Image Position

The SOP Instance creator is responsible for maintaining consistency between the actual value of the attribute listed as the Dimension Index Pointer (0020,9165) and the corresponding value in the Dimension Index Values (0020,9157) attribute.

C.7.6.17.2 Dimension Organization UID

The Dimension Organization UID (0020,9164) value identifies a set of dimensions to which an Item of the Dimension Index Sequence (0020,9222) belongs.

When different SOP Instances share the same Dimension Organization UID (0020,9164) for a particular Item of the Dimension Index Sequence (0020,9222), equivalent indices from the corresponding Dimension Index Values (0020,9157) shall have the same meaning across the SOP Instances.

This mechanism allows an image creator to explicitly specify that indices are intended to convey identical information across SOP Instances.

Dimension Organization Sequence (0020,9221) contains a summary of all the Dimension Organization UID (0020,9164) values used in a SOP Instance.

Note

Figure C.7.6.17-2 illustrates how this is used for a SOP Instance created by a multi-planar reformat application from a SOP Instance containing three Items in the Dimension Index Sequence. The meaning of the indices for Temporal Position Index (0020,9128), and MR Echo Sequence (0018,9114) were preserved in the derived SOP Instance, so it shares the Dimension Organization UID for these attributes with the original. Since the reformat was performed with a different orientation, the meaning of the In-Stack Position Number (0020,9057) was not preserved. Therefore a new Dimension Organization UID (0020,9164) was created.